The invention is related to telecommunications systems access equipment such as digital loop carriers.
Telecommunications terminals connect subscriber lines, such as POTS (Plain Old Telephone Service) and ISDN (Integrated Services Digital Network) lines, to telecommunications equipment such as a telecommunications switch, e.g., a class 5 switch. Telecommunications switches connect and route messages between different lines.
A telecommunications terminal contains channel unit card slots that accept channel unit cards. Channel unit cards convert analog and digital signals from subscriber lines into formatted digital data signals. Different types of channel unit cards service different types of subscriber lines (e.g. POTS or ISDN). The terminal constructs one or more time division multiplexed (TDM) signals from several channel unit cards"" formatted digital data signals for transmission to remote telecommunications equipment for example, another telecommunications terminal. The terminal also demultiplexes TDM signals received from remote telecommunications equipment to deliver formatted digital data back to the channel unit cards. Channel unit cards convert the formatted digital data into a form suitable for transmission over subscriber lines.
Two telecommunications terminals can be connected xe2x80x9cback-to-backxe2x80x9d to form a digital loop carrier (DLC) network. A DLC typically includes a remote terminal (RT) placed near a business or residence and a central terminal (CT) placed in a central exchange connected to a telecommunications switch. The RT and CT communicate over a single or multiple lines carrying TDM signals. This configuration connects subscribers to the telecommunications switch via the DLC. A digital loop carrier (DLC) at a central terminal (CT) includes a multiplexor which, using TDM, can multiplex multiple analog and digital signals from subscriber telephone lines into a single or multiple T1 signal. A mirror DLC located at a remote terminal (RT) can decode the multiplexed T1 signal into a form suitable for transmission over subscriber telephone lines. This data flow also occurs in the opposite direction from RT to CT.
In general, in one aspect, a telecommunications system has access terminal shelves and an intershelf bus interconnecting each access terminal shelf. Each access terminal shelf has transmission card slots. These slots are constructed to accept different types of transmission cards. Each different type of transmission card may use a different type of transmission medium to communicate with remote telecommunications equipment. The telecommunications system also includes a processor programmed to determine whether, to complete the connection, a transmission from the remote telecommunications equipment needs to be transferred via the intershelf bus to another shelf in the terminal.
In accordance with various implementations, the intershelf bus structure may be controlled by a bus controller. The intershelf bus may include two bidirectional data buses with complementary timing, a timing and synchronization bus and a control local area network. The intrashelf bus structure includes a control bus, a time division multiplexed bus and a timing bus.
A method of handling transmission in a telecommunications system having a plurality of identical shelves includes communicating with remote telecommunications equipment, accepting different types of transmissions from the remote telecommunications equipment over different types of transmission media and determining whether the accepted transmissions need to be transferred from a shelf that accepted them to another shelf via an intershelf bus structure to complete connection.
In accordance with various implementations, transferring of transmissions between shelves via the intershelf bus structure may be controlled by a bus controller. The determination of whether transmissions need to be transferred is performed by a processor residing on each shelf.
Advantages may includes one or more of the following. Telephone service providers will be able to construct a digital loop carrier without requiring an expensive master control shelf. Digital loop carriers constructed using the configurations described here are expandable on as-needed basis. Moreover, system efficiency will increase due to the distributed processing configuration. Other advantages and features will become apparent from the following description including the drawings and claims.